The manipulator for positioning a test head normally has a plurality of translational and rotational degrees of freedom in thus being suitable for precisely positioning the test head three-dimensionally. This is why, as a rule, such a manipulator finds application in testing electronic components such as, for instance, integrated circuits (ICs) or wafers. For function testing electronic components it is necessary to precisely locate the relatively heavy test head at a tester. The tester, for example as a device handler or wafer prober, presents the electronic components to the test head for testing. Obtaining a genuine test result when testing electronic components requires precise docking of the test head at the tester. This is why precise, smooth adjustment of the manipulator positioning the test head is a mandatory requirement.
DE 101 32 489 A1 describes a manipulator characterized by precise repeatability in moving the test head. This is mainly due to the manipulator being provided with positioning means for three-dimensionally positioning the test head which feature articulated links for pivoting in the horizontal plane. These articulated links (pivot links) are coupled to carriages for horizontal travel so that any motion of the test head can be split into a translational motion of the carriages and a rotational motion of the articulated links. It is in this way that the positioning means can be adjusted with precise repetition in assuring reliable positioning of the test head.
In addition, DE 40 07 011 C2 describes a manipulator featuring dual articulated links for three-dimensionally positioning a test head. The dual articulated links are linked at a first end articulated to a cradle securing the test head. At a second end the dual articulated links are articulatedly linked to a pivot link which pivots about an upright axis. The pivot link is disposed at a column enabling the pivot link to be additionally linearly positioned vertical. Although the known manipulator, because of its combination of rotational motions of the pivot link and of the dual articulated links, features manifold adjustment capabilities horizontal, repeatable adjustment is only possible with undue complication.
A manipulator serving to position a test head and featuring a cradle comprising a motion mechanism is described in WO 03/089834 A2. The motion mechanism permits implementation of an in/out motion along a first axis, a tumble motion about a second axis orthoganal to the first axis and a theta motion about a third axis orthoganal to both the first axis and also the second axis of the test head secured to the cradle. For this purpose the motion mechanism comprises a slide link which performs the horizontal motion along the first axis. The motion mechanism comprises in addition, slave actuators guided in a curved groove to permit the tumble motion about the second axis. In addition, the motion mechanism features a link swivel-mounted to permit the theta motion about the third axis. This manipulator is additionally provided with locking means for locking the motion mechanism with three degrees of freedom.
WO 02/24400 A2 also discloses a mounting unit for a test head enabling the test head to be levelled. For this purpose the mounting unit features a shiftable slider for varying the position of the test head relative to the mounting unit.
In addition to the precision of the positioning means as needed for repeat adjustment it has been discovered to be expedient to correct the position of the test head by jiggling it manually in docking it to the tester. Correcting the position of the test head in this way facilitates docking but necessitates a certain compliancy of the positioning means or cradle.
A manipulator for positioning a test head provided with a cradle for the test head which generates a certain compliancy reads from WO 2004/070400 A1. The cradle can be pivotally mounted by means of upper and lower articulated links to a bearing plate. The compliancy of the cradle is created by an adjusting mechanism provided with spring elements. The spring elements are arranged so that the cradle can be adjusted relative to the bearing plate in overcoming a return force.